[Driver] Support -fsanitize=function on Solaris/x86

UBSan-Standalone-x86_64 :: TestCases/TypeCheck/Function/function.cpp currently
FAILs on Solaris/x86_64:

  clang-9: error: unsupported option '-fsanitize=function' for target 'x86_64-pc-solaris2.11'

AFAICS, there's nothing more to do then enable that sanitizer in the driver (for x86 only),
which is what this patch does, together with updating another testcase.

Tested on x86_64-pc-solaris2.11.

Differential Revision: https://reviews.llvm.org/D64488

llvm-svn: 367351